Public transit systems in many cities may be comprised of multiple modes of transportation including buses, trains, light rails, and subways, each using various methods to receive payment for fares. In some transportation systems, a point of sale (POS) terminal may be used to purchase a ticket. Mobile devices are used in some transit systems as a means to pay a transit fare using near-field-communications (NFC).
Some stations, for example a train station, may have multiple trains all leaving from the same platform at approximately the same time. A subway system may have multiple levels of trains underground, all accessible from the same station. A bus route may require one or more transfers to reach a destination.